Conventionally, the photolithography process as one of processes for manufacturing semiconductor devices represented by semiconductor integrated circuits uses various types of exposure apparatuses to expose a circuit pattern, or the like, formed on a mask or reticle (to be referred to as a reticle hereinafter) onto a wafer coated with a photosensitive agent (photoresist).
Currently, as the semiconductor devices shrink in feature size and increase in integration density, a projection exposure apparatus or a so-called stepper, and a so-called scanning type exposure apparatus have been widely used. The projection exposure apparatus moves the irradiation region of the exposure light to expose the exposure regions of a reticle. The scanning type exposure apparatus projects a reticle pattern onto a limited band-like rectangular or arcuate region on a wafer, and scans a reticle and the wafer synchronously in a one-dimensional direction, so that the reticle pattern is transferred onto the wafer. The movable stage apparatus described above generally uses linear motors as its driving source. FIG. 6 shows a conventional movable stage apparatus (Japanese Patent Laid-Open No. 10-12539) mounted on the scanning type projection exposure apparatus described above.
The conventional movable stage apparatus is constituted by a guide 102 fixed on a reticle base 101, a reticle stage 103 reciprocally movable in a Y-axis direction (the scanning direction of the reticle stage will be defined as the Y-axis; to be referred to as the Y-axis direction hereinafter) along the guide 102, and a pair of linear motors 106a and 106b arranged on the two sides of the reticle stage 103 along its traveling path to accelerate and decelerate the reticle stage 103 in the Y-axis direction. The reticle stage 103 is guided by a hydrostatic bearing (air slide) 107 and a preload mechanism not in contact with a guide surface.
A reticle R is chucked on the reticle stage 103, and a projection optical system (not shown) is provided under the reticle stage 103. A wafer is held by a wafer stage (not shown). The wafer stage also has a driving mechanism similar to that of the reticle stage 103, and is controlled in the same manner as is the reticle stage 103.
In general, the resolution of an exposure apparatus is mainly determined by a wavelength λ of an exposing illumination light source and a numerical aperture NA of a projection optical system. More specifically, the shorter the wavelength λ of the exposing illumination light source to be used or the larger the numerical aperture NA of the projection optical system, the higher the resolution becomes. Therefore, the wavelength of the exposing illumination light source used in the exposure apparatus decreases year by year, and the numerical aperture NA of the projection optical system increases.
In a current mainstream exposure apparatus, a KrF excimer laser (λ=248 nm) or an ArF excimer laser (λ=193 nm) is used as the exposing illumination light source. An exposure apparatus that uses an F2 laser with a shorter wavelength (λ=157 nm) is also being introduced on a practical level.
To transfer a circuit pattern with a practical minimum line width of 70 nm to 100 nm or less onto a wafer, a light source with a much shorter wavelength is necessary. To meet the above demand, an EUV (Extreme Ultraviolet) exposure apparatus, which uses EUV light with a wavelength λ of about 13 nm, which is shorter than even that of the exposure illumination light source described above by one or more orders of magnitude, has been attracting attention.